1. Field of the Invention
This invention relates to rearview mirrors and, more particularly, to an electrically driving system for foldable outer rearview mirrors of a motor vehicles.
2. Description of the Prior Art
Outer rearview mirrors are suitably folded to reduce their length when parking or storing motor vehicles. Recently, there are electrically foldable outer rearview mirrors which are driven by reversible motors provided in their body. A driving device of such outer rearview mirrors includes an operation switch for switching the direction of current of the reversible motors. While the operation switch is held at a folding position, the mirrors are turned toward a folded state. On the other hand, while the switch is held at an erecting position, the mirrors are turned toward an erected state. When the mirrors are turned to a predetermined position, they can be held stationary at that position by releasing the operation switch.
There has been realized a drive system, in which relays and self-holding circuits are provided to let the motors be rotated and stopped indirectly in response to operate a switch instead of rotating and stopping the motors directly by operating a switch. Such an improved drive system is disclosed in Japanese Patent Application Laid-Open No. Sho 61-113533. In this system, a motor circuit for each of the right and left mirror bodies includes a first self-holding circuit which is rendered operative when turning the mirror body from the folded state to the erected state and a second self-holding circuit which is rendered operative when turning the mirror body from the erected state to the folded state. When the mirror body reach to either of these states, a limit switch is operated to release a self-holding state so as to automatically stop the motor. In this drive system, however, the limit switches for detecting the erected and folded states of the right and left mirrors can only render operating relays no-exciting, that is, they can not render both relays and motors inoperative. Besides, it is necessary to provide normal and reverse relays and self-holding circuits for each of the right and left reversible motors. Therefore, the overall circuit is complicated , is inevitably large in size, requires a large number of assembling steps and dictates high cost of manufacture.
An object of the invention is to provide an electrically driving system for foldable outer rearview mirrors for a motor vehicle, which is reduced in size and weight by reducing the number of relays used.
Another object of the invention is to provide an electrically driving system for foldable outer rearview mirrors, which ensures accurate erecting and folding operations and can be provided at low cost.